问不附着于活性的片段怎么弄？

提问于 2018-02-06 20:09:13

回答 10关注 0查看 805

我创建了一个小测试应用程序，它代表了我的问题。我使用ActionBarSherlock来用(Sherlock)片段实现选项卡。

我的代码：TestActivity.java

public class TestActivity extends SherlockFragmentActivity {
    private ActionBar actionBar;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setupTabs(savedInstanceState);
    }

    private void setupTabs(Bundle savedInstanceState) {
        actionBar = getSupportActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        addTab1();
        addTab2();
    }

    private void addTab1() {
        Tab tab1 = actionBar.newTab();
        tab1.setTag("1");
        String tabText = "1";
        tab1.setText(tabText);
        tab1.setTabListener(new TabListener<MyFragment>(TestActivity.this, "1", MyFragment.class));

        actionBar.addTab(tab1);
    }

    private void addTab2() {
        Tab tab1 = actionBar.newTab();
        tab1.setTag("2");
        String tabText = "2";
        tab1.setText(tabText);
        tab1.setTabListener(new TabListener<MyFragment>(TestActivity.this, "2", MyFragment.class));

        actionBar.addTab(tab1);
    }
}

TabListener.java

public class TabListener<T extends SherlockFragment> implements com.actionbarsherlock.app.ActionBar.TabListener {
    private final SherlockFragmentActivity mActivity;
    private final String mTag;
    private final Class<T> mClass;

    public TabListener(SherlockFragmentActivity activity, String tag, Class<T> clz) {
        mActivity = activity;
        mTag = tag;
        mClass = clz;
    }

    /* The following are each of the ActionBar.TabListener callbacks */

    public void onTabSelected(Tab tab, FragmentTransaction ft) {
        SherlockFragment preInitializedFragment = (SherlockFragment) mActivity.getSupportFragmentManager().findFragmentByTag(mTag);

        // Check if the fragment is already initialized
        if (preInitializedFragment == null) {
            // If not, instantiate and add it to the activity
            SherlockFragment mFragment = (SherlockFragment) SherlockFragment.instantiate(mActivity, mClass.getName());
            ft.add(android.R.id.content, mFragment, mTag);
        } else {
            ft.attach(preInitializedFragment);
        }
    }

    public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        SherlockFragment preInitializedFragment = (SherlockFragment) mActivity.getSupportFragmentManager().findFragmentByTag(mTag);

        if (preInitializedFragment != null) {
            // Detach the fragment, because another one is being attached
            ft.detach(preInitializedFragment);
        }
    }

    public void onTabReselected(Tab tab, FragmentTransaction ft) {
        // User selected the already selected tab. Usually do nothing.
    }
}

MyFragment.java

public class MyFragment extends SherlockFragment {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        new AsyncTask<Void, Void, Void>() {

            @Override
            protected Void doInBackground(Void... params) {
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException ex) {
                }
                return null;
            }

            @Override
            protected void onPostExecute(Void result){
                getResources().getString(R.string.app_name);
            }

        }.execute();
    }
}

我增加了Thread.sleep部分模拟下载数据中的代码onPostExecute是模拟使用Fragment...

当我在景物和肖像之间快速旋转屏幕时，我在onPostExecute代码：

java.lang.IllegalStateException: Fragment MyFragment{410f6060} not attached to Activity

我认为这是因为同时创建了一个新的MyFragment，并且在AsyncTask完成之前附加到Activity。 onPostExecute中的代码调用一个未连接的MyFragment。

但是我怎样才能解决这个问题？

java

fragment

测试

连接

数据

回答 10

初冬微笑已冻僵

回答已采纳

发布于 2018-02-06 20:48:38

我找到了一个非常简单的答案：isAdded():

true如果该片段当前被添加到其活动中。

@Override
protected void onPostExecute(Void result){
    if(isAdded()){
        getResources().getString(R.string.app_name);
    }
}

避免onPostExecute被调用时，Fragment没有附加到Activity是取消AsyncTask当暂停或停止Fragment.然后isAdded()不再有必要了。

Rom_z

发布于 2018-02-07 06:02:33

在我的例子中，片段方法在

getActivity().onBackPressed();

活动执行wrl

发布于 2018-02-07 04:52:37

如果你扩展Application初始化并维护一个静态的“global”上下文对象，如下所示，然后你可以使用它而不是该活动来加载字符串资源。

public class MyApplication extends Application {
    public static Context GLOBAL_APP_CONTEXT;

    @Override
    public void onCreate() {
        super.onCreate();
        GLOBAL_APP_CONTEXT = this;
    }
}